It is understood that Moscow responded to the threat by claiming it would freeze the BBC's finances in Russia and report Britain to international watchdogs for violating Russia's right to freedom of speech.

Over the next 24 hours, the bank appeared to change its mind and announced in a later statement that the decision to close Russia Today's account was under review.

“These decisions are not taken lightly," an RBS spokesman said. "We are reviewing the situation and are contacting the customer to discuss this further. The bank accounts remain open and are still operative."

Margarita Simonyan, Russia Today's editor-in-chief responded on Twitter with the sarcastic message "Praise be to freedom of speech!" before publishing a copy of the bank's letter, which described the decision of "final."

When news broke that RBS was reconsidering its decision, she added: "After yesterday's noise, the bank now says that he is ready to discuss the situation. But yesterday it wrote that it would not discuss this."

The identity of the letter's recipient was blanked out but is believed to have been addressed to one of Russia Today's suppliers, not the station itself.

Theresa May, the British prime minister, was accused of sitting on the fence about the issue after her spokesman said it was a matter for the bank.

Russia Today has faced accusations in the past of broadcasting propaganda on Putin's behalf.

A spokesman for Russia's Information and Press Department said: "Russia is deeply concerned about the closure of the UK bank accounts belonging to the RT TV channel's London office, a decision that takes effect on December 12, 2016.

"This news was published today and announced in a letter by the National Westminster Bank dated October 12, 2016.

"The resulting situation presents formidable barriers for the TV channel’s normal operation in the UK, which creates the preconditions to consider the bank’s step as coordinated with London in an attempt to get rid of a news source embarrassing for the British establishment but popular with the British public.

"If this is true, it is a crude violation of the freedom of speech and the press on the part of 'one of the oldest democracies in the world' as the British people call themselves.

"We will demand that the British authorities explain the current situation in the near future."

It is understood that the account will be frozen in 60 days if RBS sticks to its its initial decision to close it.